The most stressful situation for a battery's working environment is to be under a constant and heavy load. This is exactly the characteristic of an electric vehicle application. A battery with an intermittent load allows a level of electrochemical recovery during periods of very low or zero load. This is especially evident in Lead Acid cells but is a feature of all cell chemistries. Because of the time-constant associated with this behavior, a quiescent rest period is especially beneficial in extending the operating lifetime. A redundant cell isolation philosophy enables this recovery.
In an electric vehicle application there is a requirement for an additional motor speed controller to respond to demands from the throttle system. These units are relatively bulky and represent an increase in weight and cost which is particularly significant for a light electric vehicle or electric bike. A cell bypass system can replicate this function without need for the additional component, offering significant savings in both cost and weight.
A Photovoltaic array operated under lower light conditions such as in Northern latitudes or on an overcast day for example may not achieve the output voltage required to charge a battery system. If some of the cells are bypassed however to lower the battery voltage it may be possible to capture power in less than ideal circumstances.
Detailed descriptions regarding a controlling system and method about battery powered device are disclosed in other documents such as U.S. Pat. No. 6,744,698 by Shunsuke Koyama et al. Shunsuke Koyama et al disclose that when a battery is used for an extended period, characteristics deteriorate and the internal resistance in particular increases. Shunsuke Koyama et al further disclose an electronic device which comprises: a battery, a plurality of load groups, a first control unit and a second control unit. The load groups includes a heavy load group that is comprised of a plurality of heavy load units driven by the battery and a light load group that is comprised of a plurality of light load units and that consumes less power than the heavy load group. When the output voltage of the battery drops below the first threshold voltage, the first control unit (i) stops monitoring the output voltage of the battery, (ii) disables the supply of power from the battery to the heavy load group, the disabled power state of the heavy load group being maintained regardless of any future change in the output voltage of the power supply, and (iii) outputs an activation signal to activate the second control unit. The system and method described by Shunsuke Koyama et al can stop driving the heavy load unit with the battery when the battery output voltage drops to the threshold voltage and give the battery some time for recovery. But Shunsuke Koyama et al do not disclose or suggest a system or method that can be applied for managing a plurality of battery cells connected with each other in series, especially in light electric vehicles.